A variety of herbicides have been hitherto developed and contributed to the productivity and labor-saving in agriculture. However, certain kinds of herbicides have been used over so long years that population of troublesome weeds withstanding them are increasing so that appearance is desired of a herbicids having a broad herbicidal spectrum and effectiveness also against these troublesome weeds. It is also desired to develop a high-activity herbicide in order to overcome the problem of environmental pollution by conventional herbicides. In order to overcome to the problem of the ununiform germination of weeds over a long period of time, furthermore, appearance is also awaited of a herbicide exhibiting excellent persistent effectiveness and having a versatility of treatment to exhibit effectiveness even by treatment over a wide range of period from the pre-germination stage to the growing period of weeds.
The inventors have continued investigations to develop a herbicide capable of exhibiting an excellent herbicidal effect against various kinds of annual and perennial weeds without causing phytotoxicity to paddy rice and arrived at a discovery that a herbicide containing a triazine compound as an effective ingredient is effective (official publication of Japanese Patent Toku-sai-hyo 88/02368, official publication of Japanese Patent Kokai 63-146876, official publication of Japanese Patent Kokai 63-51379 and official publication of Japanese Patent Kokai 63-264465). This triazine-based herbicide is highly active against troublesome weeds in paddy rice field at low dosage without phytotoxicity to-paddy rice plant. This herbicide also shows excellent herbicidal activity against troublesome weeds by foliage application in upland field without phytotoxicity to Gramineous crops.
Nevertheless, this herbicide shows somewhat limited performance by preemergence treatment to the soil in upland fields.